[OSRS-PROJ] Rectified Skew Orthomorphic...EPSG

[Clifford J Mugnier]

Gerald,

If memory serves me correctly, gamma is a function in Hotine's original
papers in "Empire Survey Review" that in actuality is "hard-coded" into the
projection equations used for Borneo and Malaya.  I'm not certain, though.

The EPSG math documentation is essentially a monograph by Mr. Roger Lott,
Retired Chief Surveyor for British Petroleum.  I believe his old company
e-mail address is still active.  It is lottrj at BP.com and this was a
near-religious pursuit for him in his later years at BP.  I am certain he
would be delighted to discuss the matter with you.  I am cc-ing him with
this so that he has a "heads up."




Sorry to be slow in finishing this problem but still in the process of
trying
to resolve the loose ends in this muddy projection.

PJ_omerc reproduces test values for the EPSG #7 example and
a variety of comparisons with GCTP.  I am satisfied that the procedure
is functioning properly.

However, resolving the documentation has not been so easy.
I am being careful that the doc math agrees with what the software
does.  The major problem is that EPSG #7 threw me off several times
and I am now fairly certain that some parts of it are wrong---even
though the example does compute.

Additional test were made with numbers for the Borneo RSO kindly
provided by Godkin.  PJ_omerc agreed within a few centimeters with
Godkin's number but the errors were random in sign and magnitude
and indicated to me that there was a precision problem with the
computation of his values rather than an  algorithmic difference that
would have yielded more consistent deviations.

I would like to make trials with other data.

Secondly, is there a contact with EPSG that is involved with
preparing #7.  I think we should get together on this issue.

I did run into a data base supposedly from EPSG that listed proj
options for both Borneo and Malaya but while both included
azimuth "alpha" neither included the required "gamma_c."
_____________________________________
Jerry and the low riders: Daisy Mae and Joshua

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